Hydrocyclone separators are known to be useful for the classification or fractionation of coarse from fine solids suspended in a liquid. In general, a hydrocyclone is an enclosed vortical machine usually comprising a short cylindrical section followed by a conical section. Feed of a suspension of solids is supplied under predetermined pressure tangentially or in a volute path into the head part so as to create therein a swirling stream of fluid, which stream follows a path of gradually decreasing radius toward the point of the narrowest radius of the cone, commonly known as the apex.
As the spiral path approaches the apex of the hydrocyclone, a portion of it turns and begins to flow towards the opposite end, i.e. towards the cylindrical section. Also this flow is in a spiral path of radius smaller than the radius of the first spiral while rotating in the same direction. Thus a vortex is generated within the hydrocyclone. The pressure will be lower along the central axis of the vortex and increase radially outwardly. The idea is that the hydrocyclone will separate the particles of the slurry according to shape, size and specific gravity with faster settling particles moving towards the outer wall of the hydrocyclone eventually leaving the hydrocyclone through the apex discharge port. Slower settling particles will move towards the central axis and travel upwardly, eventually leaving the hydrocyclone through the overflow discharge tube. The discharge tube is normally extending down into the cylindrical section such that shortcircuiting of the feed is prevented.
The efficiency of this operation, that is the sharpness of the separation of the coarser from the finer particles, depends on the size of the apex opening, the feed speed, and the density of the material to be separated and classified. Also the length of the conical section from the cylindrical part to the apex opening will have an impact on the operation of the separation and/or classification.
During operation the inner lining of the hydrocyclone separator will wear, and this is also true for the lining within the apex opening. This has the consequence that one of the parameters which influence the outcome of the separation and/or classification will not be constant during operation. Accordingly, the separation and/or classification will not be consistent during the operation of the hydrocyclone. Further, the apex opening has a tendency to plug during operation, and there may be a need to prevent or elevate any such condition.
GB 889,253 discloses a hydrocyclone having an adjustable discharge orifice. The arrangement of the adjustable discharge orifice according to GB 889,253 adjusts the discharge orifice size, but at the same time the discharge orifice will be moved in axial direction, changing the conical length from the head part and down to the discharge orifice. Thus, even if wear and/or plugging may be compensated for or elevated, one of the main parameters for the classification and/or separation is also changed.